1. Field of the Invention
The present invention relates to a semiconductor storage device for use in personal authentication or the like. More particularly, it relates to a semiconductor storage device to which an engineering neuron model is applied.
2. Description of the Related Art
In recent years, security devices concerning personal information, for example, an IC card and a fingerprint authentication device for biometric authentication have increased. In the IC card having a security function, there are various approaches concerning technologies for encrypting an input signal or preventing the theft of data. For example, as to the encryption, sophisticated encryption algorithms such as RSA and elliptic function can be used to improve reliability. However, from the viewpoint of power reduction, it is not realistic to mount these complicated algorithms on miniaturized devices.
As an encryption technology for the reduction of power consumption, a device using a neuron model has been investigated. In the device in which the neuron model is used, registered data are subjected to weighted coupling (encrypted). In this kind of device, reverse reading is more difficult than in a case of simple conversion into electrical signals, and hence the device has the function of data theft prevention.
As the devices in which the neuron model is used, a neuron MOS (e.g., see Tadashi Shibata, Jpn. J. App. Phys., Vol. 72, No. 10, [2003]) and a circuit including a resistor and an inverter (e.g., see R. E. Howard, et al., ED, 34, 1553 (1987)) have heretofore been suggested. However, the device referred to as the neuron MOS has a structure in which several floating gates are formed under a single gate, so that it is difficult to directly control the charge state of each floating gate. In the circuit including the resistor and the inverter, a large resistance change is required, which increases the power consumption. Furthermore, in these structures, there is a problem that a coupling weight can be updated, but cannot be stored or held.
Therefore, the miniaturization of the security device is intended, and a semiconductor storage device is demanded in which the coupling weight of the neuron model can be stored.